title: Increased 1,25-dihydroxyvitamin D3 synthesis in rats fed a high-phosphorus diet.
abstract: Rats fed vitamin D-deficient diets containing 0.6% Ca and 0.3%, 0.6%, 1.2%, or 1.8% P exhibited progressive increments of hypocalcemia and hyperphosphatemia. In vitro assay of 25-hydroxyvitamin D3-1-alpha-hydroxylase (1-alpha-hydroxylase) activity in isolated kidney cortical mitochondria showed that hyperphosphatemia in the presence of hypocalcemia was associated with an increase in enzyme activity. The results indicate that the stimulation of 1-alpha-hydroxylase associated with depressed plasma Ca in rats fed a high-P diet overrides any inhibition of the enzyme that may be caused by excess plasma phosphate.
mesh_terms: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; D000818:Animals; D002112:Calcifediol; D002117:Calcitriol / Q000096:biosynthesis*; D002118:Calcium / Q000097:blood; D004032:Diet; D006887:Hydroxycholecalciferols / Q000494:pharmacology; D006996:Hypocalcemia / Q000378:metabolism; D007672:Kidney Cortex / Q000201:enzymology; D008297:Male; D010710:Phosphates / Q000097:blood*; D010758:Phosphorus / Q000008:administration & dosage*; D051381:Rats; D011919:Rats, Inbred Strains; D013250:Steroid Hydroxylases / Q000378:metabolism*; D014808:Vitamin D Deficiency / Q000378:metabolism
chemical_list: D006887:Hydroxycholecalciferols; D010710:Phosphates; D010758:Phosphorus; D013250:Steroid Hydroxylases; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; D002117:Calcitriol; D002112:Calcifediol; D002118:Calcium